2019-01-15 18:28:24 +01:00
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/*
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SPDX-License-Identifier: GPL-2.0-only
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2019-01-18 19:42:37 +01:00
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Copyright (C) 2019 Facebook
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2019-01-15 18:28:24 +01:00
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*/
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2018-03-06 01:53:50 +01:00
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#ifndef _LIBBTF_H
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#define _LIBBTF_H
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#include "gobuffer.h"
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2018-09-13 18:19:40 +02:00
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#include <stdbool.h>
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2018-03-06 01:53:50 +01:00
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#include <stdint.h>
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2019-02-14 14:47:32 +01:00
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struct btf_elf {
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2018-03-06 01:53:50 +01:00
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union {
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struct btf_header *hdr;
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void *data;
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};
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void *priv;
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Elf *elf;
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GElf_Ehdr ehdr;
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btf_encoder: Teach pahole to store percpu variables in vmlinux BTF.
On SMP systems, the global percpu variables are placed in a special
'.data..percpu' section, which is stored in a segment whose initial
address is set to 0, the addresses of per-CPU variables are relative
positive addresses [1].
This patch extracts these variables from vmlinux and places them with
their type information in BTF. More specifically, when BTF is encoded,
we find the index of the '.data..percpu' section and then traverse the
symbol table to find those global objects which are in this section.
For each of these objects, we push a BTF_KIND_VAR into the types buffer,
and a BTF_VAR_SECINFO into another buffer, percpu_secinfo. When all the
CUs have finished processing, we push a BTF_KIND_DATASEC into the
btfe->types buffer, followed by the percpu_secinfo's content.
In a v5.8-rc3 linux kernel, I was able to extract 288 such variables.
The build time overhead is small and the space overhead is also small.
See testings below.
A found variable can be invalid in two ways:
- Its name found in elf_sym__name is invalid.
- Its size identified by elf_sym__size is 0.
In either case, the BTF containing such symbols will be rejected by the
BTF verifier. Normally we should not see such symbols. But if one is
seen during BTF encoding, the encoder will exit with error. An new flag
'-j' (or '--force') is implemented to help testing, which skips the
invalid symbols and force emit a BTF.
Testing:
- vmlinux size has increased by ~12kb.
Before:
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d2bf8 00
After:
$ pahole -J vmlinux
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d5bca 00
- Common global percpu VARs and DATASEC are found in BTF section.
$ bpftool btf dump file vmlinux | grep runqueues
[14152] VAR 'runqueues' type_id=13778, linkage=global-alloc
$ bpftool btf dump file vmlinux | grep 'cpu_stopper'
[17582] STRUCT 'cpu_stopper' size=72 vlen=5
[17601] VAR 'cpu_stopper' type_id=17582, linkage=static
$ bpftool btf dump file vmlinux | grep ' DATASEC '
[63652] DATASEC '.data..percpu' size=179288 vlen=288
- Tested bpf selftests.
- pahole exits with error if an invalid symbol is seen during encoding,
make -f Makefile -j 36 -s
PAHOLE: Error: Found symbol of zero size when encoding btf (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Error: Use '-j' or '--force_emit' to ignore such symbols and force emit the btf.
scripts/link-vmlinux.sh: line 137: 2475712 Segmentation fault LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
- With the flag '-j' or '--force', the invalid symbols are ignored.
- Further in verbose mode and with '-j' or '--force' set, a warning is generated:
PAHOLE: Warning: Found symbol of zero size when encoding btf, ignored (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Warning: Found symbol of invalid name when encoding btf, ignored (sym: 'zzz', cu: 'sss.c').
References:
[1] https://lwn.net/Articles/531148/
Signed-off-by: Hao Luo <haoluo@google.com>
Tested-by: Andrii Nakryiko <andriin@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Oleg Rombakh <olegrom@google.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-07-08 22:44:10 +02:00
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struct elf_symtab *symtab;
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2018-03-06 01:53:50 +01:00
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struct gobuffer types;
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struct gobuffer *strings;
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btf_encoder: Teach pahole to store percpu variables in vmlinux BTF.
On SMP systems, the global percpu variables are placed in a special
'.data..percpu' section, which is stored in a segment whose initial
address is set to 0, the addresses of per-CPU variables are relative
positive addresses [1].
This patch extracts these variables from vmlinux and places them with
their type information in BTF. More specifically, when BTF is encoded,
we find the index of the '.data..percpu' section and then traverse the
symbol table to find those global objects which are in this section.
For each of these objects, we push a BTF_KIND_VAR into the types buffer,
and a BTF_VAR_SECINFO into another buffer, percpu_secinfo. When all the
CUs have finished processing, we push a BTF_KIND_DATASEC into the
btfe->types buffer, followed by the percpu_secinfo's content.
In a v5.8-rc3 linux kernel, I was able to extract 288 such variables.
The build time overhead is small and the space overhead is also small.
See testings below.
A found variable can be invalid in two ways:
- Its name found in elf_sym__name is invalid.
- Its size identified by elf_sym__size is 0.
In either case, the BTF containing such symbols will be rejected by the
BTF verifier. Normally we should not see such symbols. But if one is
seen during BTF encoding, the encoder will exit with error. An new flag
'-j' (or '--force') is implemented to help testing, which skips the
invalid symbols and force emit a BTF.
Testing:
- vmlinux size has increased by ~12kb.
Before:
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d2bf8 00
After:
$ pahole -J vmlinux
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d5bca 00
- Common global percpu VARs and DATASEC are found in BTF section.
$ bpftool btf dump file vmlinux | grep runqueues
[14152] VAR 'runqueues' type_id=13778, linkage=global-alloc
$ bpftool btf dump file vmlinux | grep 'cpu_stopper'
[17582] STRUCT 'cpu_stopper' size=72 vlen=5
[17601] VAR 'cpu_stopper' type_id=17582, linkage=static
$ bpftool btf dump file vmlinux | grep ' DATASEC '
[63652] DATASEC '.data..percpu' size=179288 vlen=288
- Tested bpf selftests.
- pahole exits with error if an invalid symbol is seen during encoding,
make -f Makefile -j 36 -s
PAHOLE: Error: Found symbol of zero size when encoding btf (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Error: Use '-j' or '--force_emit' to ignore such symbols and force emit the btf.
scripts/link-vmlinux.sh: line 137: 2475712 Segmentation fault LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
- With the flag '-j' or '--force', the invalid symbols are ignored.
- Further in verbose mode and with '-j' or '--force' set, a warning is generated:
PAHOLE: Warning: Found symbol of zero size when encoding btf, ignored (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Warning: Found symbol of invalid name when encoding btf, ignored (sym: 'zzz', cu: 'sss.c').
References:
[1] https://lwn.net/Articles/531148/
Signed-off-by: Hao Luo <haoluo@google.com>
Tested-by: Andrii Nakryiko <andriin@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Oleg Rombakh <olegrom@google.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-07-08 22:44:10 +02:00
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struct gobuffer percpu_secinfo;
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2018-03-06 01:53:50 +01:00
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char *filename;
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size_t size;
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int swapped;
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int in_fd;
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uint8_t wordsize;
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2018-09-13 18:19:40 +02:00
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bool is_big_endian;
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btf loader: Support raw BTF as available in /sys/kernel/btf/vmlinux
Be it automatically when no -F option is passed and
/sys/kernel/btf/vmlinux is available, or when /sys/kernel/btf/vmlinux is
passed as the filename to the tool, i.e.:
$ pahole -C list_head
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
$ strace -e openat pahole -C list_head |& grep /sys/kernel/btf/
openat(AT_FDCWD, "/sys/kernel/btf/vmlinux", O_RDONLY) = 3
$
$ pahole -C list_head /sys/kernel/btf/vmlinux
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
$
If one wants to grab the matching vmlinux to use its DWARF info instead,
which is useful to compare the results with what we have from BTF, for
instance, its just a matter of using '-F dwarf'.
This in turn shows something that at first came as a surprise, but then
has a simple explanation:
For very common data structures, that will probably appear in all of the
DWARF CUs (Compilation Units), like 'struct list_head', using '-F dwarf'
is faster:
[acme@quaco pahole]$ perf stat -e cycles pahole -F btf -C list_head > /dev/null
Performance counter stats for 'pahole -F btf -C list_head':
45,722,518 cycles:u
0.023717300 seconds time elapsed
0.016474000 seconds user
0.007212000 seconds sys
[acme@quaco pahole]$ perf stat -e cycles pahole -F dwarf -C list_head > /dev/null
Performance counter stats for 'pahole -F dwarf -C list_head':
14,170,321 cycles:u
0.006668904 seconds time elapsed
0.005562000 seconds user
0.001109000 seconds sys
[acme@quaco pahole]$
But for something that is more specific to a subsystem, the DWARF loader
will have to process way more stuff till it gets to that struct:
$ perf stat -e cycles pahole -F dwarf -C tcp_sock > /dev/null
Performance counter stats for 'pahole -F dwarf -C tcp_sock':
31,579,795,238 cycles:u
8.332272930 seconds time elapsed
8.032124000 seconds user
0.286537000 seconds sys
$
While using the BTF loader the time should be constant, as it loads
everything from /sys/kernel/btf/vmlinux:
$ perf stat -e cycles pahole -F btf -C tcp_sock > /dev/null
Performance counter stats for 'pahole -F btf -C tcp_sock':
48,823,488 cycles:u
0.024102760 seconds time elapsed
0.012035000 seconds user
0.012046000 seconds sys
$
Above I used '-F btf' just to show that it can be used, but its not
really needed, i.e. those are equivalent:
$ strace -e openat pahole -F btf -C list_head |& grep /sys/kernel/btf/vmlinux
openat(AT_FDCWD, "/sys/kernel/btf/vmlinux", O_RDONLY) = 3
$ strace -e openat pahole -C list_head |& grep /sys/kernel/btf/vmlinux
openat(AT_FDCWD, "/sys/kernel/btf/vmlinux", O_RDONLY) = 3
$
The btf_raw__load() function that ends up being grafted into the
preexisting btf_elf routines was based on libbpf's btf_load_raw().
Acked-by: Alexei Starovoitov <ast@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-01-02 19:22:23 +01:00
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bool raw_btf; // "/sys/kernel/btf/vmlinux"
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2018-03-06 01:53:50 +01:00
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uint32_t type_index;
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btf_encoder: Teach pahole to store percpu variables in vmlinux BTF.
On SMP systems, the global percpu variables are placed in a special
'.data..percpu' section, which is stored in a segment whose initial
address is set to 0, the addresses of per-CPU variables are relative
positive addresses [1].
This patch extracts these variables from vmlinux and places them with
their type information in BTF. More specifically, when BTF is encoded,
we find the index of the '.data..percpu' section and then traverse the
symbol table to find those global objects which are in this section.
For each of these objects, we push a BTF_KIND_VAR into the types buffer,
and a BTF_VAR_SECINFO into another buffer, percpu_secinfo. When all the
CUs have finished processing, we push a BTF_KIND_DATASEC into the
btfe->types buffer, followed by the percpu_secinfo's content.
In a v5.8-rc3 linux kernel, I was able to extract 288 such variables.
The build time overhead is small and the space overhead is also small.
See testings below.
A found variable can be invalid in two ways:
- Its name found in elf_sym__name is invalid.
- Its size identified by elf_sym__size is 0.
In either case, the BTF containing such symbols will be rejected by the
BTF verifier. Normally we should not see such symbols. But if one is
seen during BTF encoding, the encoder will exit with error. An new flag
'-j' (or '--force') is implemented to help testing, which skips the
invalid symbols and force emit a BTF.
Testing:
- vmlinux size has increased by ~12kb.
Before:
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d2bf8 00
After:
$ pahole -J vmlinux
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d5bca 00
- Common global percpu VARs and DATASEC are found in BTF section.
$ bpftool btf dump file vmlinux | grep runqueues
[14152] VAR 'runqueues' type_id=13778, linkage=global-alloc
$ bpftool btf dump file vmlinux | grep 'cpu_stopper'
[17582] STRUCT 'cpu_stopper' size=72 vlen=5
[17601] VAR 'cpu_stopper' type_id=17582, linkage=static
$ bpftool btf dump file vmlinux | grep ' DATASEC '
[63652] DATASEC '.data..percpu' size=179288 vlen=288
- Tested bpf selftests.
- pahole exits with error if an invalid symbol is seen during encoding,
make -f Makefile -j 36 -s
PAHOLE: Error: Found symbol of zero size when encoding btf (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Error: Use '-j' or '--force_emit' to ignore such symbols and force emit the btf.
scripts/link-vmlinux.sh: line 137: 2475712 Segmentation fault LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
- With the flag '-j' or '--force', the invalid symbols are ignored.
- Further in verbose mode and with '-j' or '--force' set, a warning is generated:
PAHOLE: Warning: Found symbol of zero size when encoding btf, ignored (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Warning: Found symbol of invalid name when encoding btf, ignored (sym: 'zzz', cu: 'sss.c').
References:
[1] https://lwn.net/Articles/531148/
Signed-off-by: Hao Luo <haoluo@google.com>
Tested-by: Andrii Nakryiko <andriin@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Oleg Rombakh <olegrom@google.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-07-08 22:44:10 +02:00
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uint32_t percpu_shndx;
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uint64_t percpu_base_addr;
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2018-03-06 01:53:50 +01:00
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};
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2019-02-14 14:47:32 +01:00
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extern uint8_t btf_elf__verbose;
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#define btf_elf__verbose_log(fmt, ...) { if (btf_elf__verbose) printf(fmt, __VA_ARGS__); }
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2018-03-06 01:53:50 +01:00
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btf_encoder: Teach pahole to store percpu variables in vmlinux BTF.
On SMP systems, the global percpu variables are placed in a special
'.data..percpu' section, which is stored in a segment whose initial
address is set to 0, the addresses of per-CPU variables are relative
positive addresses [1].
This patch extracts these variables from vmlinux and places them with
their type information in BTF. More specifically, when BTF is encoded,
we find the index of the '.data..percpu' section and then traverse the
symbol table to find those global objects which are in this section.
For each of these objects, we push a BTF_KIND_VAR into the types buffer,
and a BTF_VAR_SECINFO into another buffer, percpu_secinfo. When all the
CUs have finished processing, we push a BTF_KIND_DATASEC into the
btfe->types buffer, followed by the percpu_secinfo's content.
In a v5.8-rc3 linux kernel, I was able to extract 288 such variables.
The build time overhead is small and the space overhead is also small.
See testings below.
A found variable can be invalid in two ways:
- Its name found in elf_sym__name is invalid.
- Its size identified by elf_sym__size is 0.
In either case, the BTF containing such symbols will be rejected by the
BTF verifier. Normally we should not see such symbols. But if one is
seen during BTF encoding, the encoder will exit with error. An new flag
'-j' (or '--force') is implemented to help testing, which skips the
invalid symbols and force emit a BTF.
Testing:
- vmlinux size has increased by ~12kb.
Before:
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d2bf8 00
After:
$ pahole -J vmlinux
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d5bca 00
- Common global percpu VARs and DATASEC are found in BTF section.
$ bpftool btf dump file vmlinux | grep runqueues
[14152] VAR 'runqueues' type_id=13778, linkage=global-alloc
$ bpftool btf dump file vmlinux | grep 'cpu_stopper'
[17582] STRUCT 'cpu_stopper' size=72 vlen=5
[17601] VAR 'cpu_stopper' type_id=17582, linkage=static
$ bpftool btf dump file vmlinux | grep ' DATASEC '
[63652] DATASEC '.data..percpu' size=179288 vlen=288
- Tested bpf selftests.
- pahole exits with error if an invalid symbol is seen during encoding,
make -f Makefile -j 36 -s
PAHOLE: Error: Found symbol of zero size when encoding btf (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Error: Use '-j' or '--force_emit' to ignore such symbols and force emit the btf.
scripts/link-vmlinux.sh: line 137: 2475712 Segmentation fault LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
- With the flag '-j' or '--force', the invalid symbols are ignored.
- Further in verbose mode and with '-j' or '--force' set, a warning is generated:
PAHOLE: Warning: Found symbol of zero size when encoding btf, ignored (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Warning: Found symbol of invalid name when encoding btf, ignored (sym: 'zzz', cu: 'sss.c').
References:
[1] https://lwn.net/Articles/531148/
Signed-off-by: Hao Luo <haoluo@google.com>
Tested-by: Andrii Nakryiko <andriin@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Oleg Rombakh <olegrom@google.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-07-08 22:44:10 +02:00
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#define PERCPU_SECTION ".data..percpu"
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2018-03-06 01:53:50 +01:00
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struct base_type;
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btf: add func_proto support
Two new btf kinds, BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO,
have been added in kernel since
https://patchwork.ozlabs.org/cover/1000176/
to support better func introspection.
Currently, for a DW_TAG_subroutine_type dwarf type,
a simple "void *" is generated instead of real subroutine type.
This patch teaches pahole to generate BTF_KIND_FUNC_PROTO
properly. After this patch, pahole should have complete
type coverage for C frontend with types a bpf program cares.
For example,
$ cat t1.c
typedef int __int32;
struct t1 {
int a1;
int (*f1)(char p1, __int32 p2);
} g1;
$ cat t2.c
typedef int __int32;
struct t2 {
int a2;
int (*f2)(char q1, __int32 q2, ...);
int (*f3)();
} g2;
int main() { return 0; }
$ gcc -O2 -o t1 -g t1.c t2.c
$ pahole -JV t1
File t1:
[1] TYPEDEF __int32 type_id=2
[2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[3] STRUCT t1 kind_flag=0 size=16 vlen=2
a1 type_id=2 bits_offset=0
f1 type_id=6 bits_offset=64
[4] FUNC_PROTO (anon) return=2 args=(5 (anon), 1 (anon))
[5] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[6] PTR (anon) type_id=4
[7] TYPEDEF __int32 type_id=8
[8] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
[9] STRUCT t2 kind_flag=0 size=24 vlen=3
a2 type_id=8 bits_offset=0
f2 type_id=12 bits_offset=64
f3 type_id=14 bits_offset=128
[10] FUNC_PROTO (anon) return=8 args=(11 (anon), 7 (anon), vararg)
[11] INT char size=1 bit_offset=0 nr_bits=8 encoding=(none)
[12] PTR (anon) type_id=10
[13] FUNC_PROTO (anon) return=8 args=(vararg)
[14] PTR (anon) type_id=13
$
In the above example, type [4], [10] and [13] represent the
func_proto types.
BTF_KIND_FUNC, which represents a real subprogram, is not generated in
this patch and will be considered later.
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2018-12-18 23:09:42 +01:00
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struct ftype;
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2018-03-06 01:53:50 +01:00
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2019-02-14 14:47:32 +01:00
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struct btf_elf *btf_elf__new(const char *filename, Elf *elf);
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2019-02-14 15:03:31 +01:00
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void btf_elf__delete(struct btf_elf *btf);
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2018-03-06 01:53:50 +01:00
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2019-02-14 14:47:32 +01:00
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int32_t btf_elf__add_base_type(struct btf_elf *btf, const struct base_type *bt);
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int32_t btf_elf__add_ref_type(struct btf_elf *btf, uint16_t kind, uint32_t type,
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uint32_t name, bool kind_flag);
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int btf_elf__add_member(struct btf_elf *btf, uint32_t name, uint32_t type, bool kind_flag,
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uint32_t bitfield_size, uint32_t bit_offset);
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int32_t btf_elf__add_struct(struct btf_elf *btf, uint8_t kind, uint32_t name,
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bool kind_flag, uint32_t size, uint16_t nr_members);
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int32_t btf_elf__add_array(struct btf_elf *btf, uint32_t type, uint32_t index_type,
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uint32_t nelems);
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int32_t btf_elf__add_enum(struct btf_elf *btf, uint32_t name, uint32_t size,
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uint16_t nr_entries);
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int btf_elf__add_enum_val(struct btf_elf *btf, uint32_t name, int32_t value);
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int32_t btf_elf__add_func_proto(struct btf_elf *btf, struct ftype *ftype,
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uint32_t type_id_off);
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btf_encoder: Teach pahole to store percpu variables in vmlinux BTF.
On SMP systems, the global percpu variables are placed in a special
'.data..percpu' section, which is stored in a segment whose initial
address is set to 0, the addresses of per-CPU variables are relative
positive addresses [1].
This patch extracts these variables from vmlinux and places them with
their type information in BTF. More specifically, when BTF is encoded,
we find the index of the '.data..percpu' section and then traverse the
symbol table to find those global objects which are in this section.
For each of these objects, we push a BTF_KIND_VAR into the types buffer,
and a BTF_VAR_SECINFO into another buffer, percpu_secinfo. When all the
CUs have finished processing, we push a BTF_KIND_DATASEC into the
btfe->types buffer, followed by the percpu_secinfo's content.
In a v5.8-rc3 linux kernel, I was able to extract 288 such variables.
The build time overhead is small and the space overhead is also small.
See testings below.
A found variable can be invalid in two ways:
- Its name found in elf_sym__name is invalid.
- Its size identified by elf_sym__size is 0.
In either case, the BTF containing such symbols will be rejected by the
BTF verifier. Normally we should not see such symbols. But if one is
seen during BTF encoding, the encoder will exit with error. An new flag
'-j' (or '--force') is implemented to help testing, which skips the
invalid symbols and force emit a BTF.
Testing:
- vmlinux size has increased by ~12kb.
Before:
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d2bf8 00
After:
$ pahole -J vmlinux
$ readelf -SW vmlinux | grep BTF
[25] .BTF PROGBITS ffffffff821a905c 13a905c 2d5bca 00
- Common global percpu VARs and DATASEC are found in BTF section.
$ bpftool btf dump file vmlinux | grep runqueues
[14152] VAR 'runqueues' type_id=13778, linkage=global-alloc
$ bpftool btf dump file vmlinux | grep 'cpu_stopper'
[17582] STRUCT 'cpu_stopper' size=72 vlen=5
[17601] VAR 'cpu_stopper' type_id=17582, linkage=static
$ bpftool btf dump file vmlinux | grep ' DATASEC '
[63652] DATASEC '.data..percpu' size=179288 vlen=288
- Tested bpf selftests.
- pahole exits with error if an invalid symbol is seen during encoding,
make -f Makefile -j 36 -s
PAHOLE: Error: Found symbol of zero size when encoding btf (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Error: Use '-j' or '--force_emit' to ignore such symbols and force emit the btf.
scripts/link-vmlinux.sh: line 137: 2475712 Segmentation fault LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
- With the flag '-j' or '--force', the invalid symbols are ignored.
- Further in verbose mode and with '-j' or '--force' set, a warning is generated:
PAHOLE: Warning: Found symbol of zero size when encoding btf, ignored (sym: 'yyy', cu: 'xxx.c').
PAHOLE: Warning: Found symbol of invalid name when encoding btf, ignored (sym: 'zzz', cu: 'sss.c').
References:
[1] https://lwn.net/Articles/531148/
Signed-off-by: Hao Luo <haoluo@google.com>
Tested-by: Andrii Nakryiko <andriin@fb.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Oleg Rombakh <olegrom@google.com>
Cc: dwarves@vger.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-07-08 22:44:10 +02:00
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int32_t btf_elf__add_var_type(struct btf_elf *btfe, uint32_t type, uint32_t name_off,
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uint32_t linkage);
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int32_t btf_elf__add_var_secinfo(struct gobuffer *buf, uint32_t type,
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uint32_t offset, uint32_t size);
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int32_t btf_elf__add_datasec_type(struct btf_elf *btfe, const char *section_name,
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struct gobuffer *var_secinfo_buf);
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2019-02-14 14:47:32 +01:00
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void btf_elf__set_strings(struct btf_elf *btf, struct gobuffer *strings);
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int btf_elf__encode(struct btf_elf *btf, uint8_t flags);
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2018-03-06 01:53:50 +01:00
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2019-02-14 14:47:32 +01:00
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char *btf_elf__string(struct btf_elf *btf, uint32_t ref);
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int btf_elf__load(struct btf_elf *btf);
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btf_loader: Introduce a loader for the BTF format
Show 'struct list_head' from DWARF info:
$ pahole -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
Try to show it from BTF, on a file without it:
$ pahole -F btf -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
pahole: /home/acme/git/build/v4.20-rc5+/net/ipv4/tcp.o: No debugging information found
Encode BTF from the DWARF info:
$ pahole -J ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
Check that it is there:
$ readelf -SW ~/git/build/v4.20-rc5+/net/ipv4/tcp.o | grep BTF
readelf: /home/acme/git/build/v4.20-rc5+/net/ipv4/tcp.o: Warning: possibly corrupt ELF header - it has a non-zero program header offset, but no program headers
[136] .BTF PROGBITS 0000000000000000 101d0e 042edf 00 0 0 1
Now try again printing 'struct list_head' from the BTF info just
encoded:
$ pahole -F btf -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o 2> /dev/null
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
$
There is the bitfields case that BTF desn't have the bit_size info for
bitfield members that makes the output from dwarf to be different than
the one from BTF:
$ pahole -F btf -C sk_buff ~/git/build/v4.20-rc5+/net/ipv4/tcp.o > /tmp/sk_buff.btf
$ pahole -F dwarf -C sk_buff ~/git/build/v4.20-rc5+/net/ipv4/tcp.o > /tmp/sk_buff.dwarf
$ diff -u /tmp/sk_buff.dwarf /tmp/sk_buff.btf
--- /tmp/sk_buff.dwarf 2018-12-20 14:50:51.428653046 -0300
+++ /tmp/sk_buff.btf 2018-12-20 14:50:46.302601516 -0300
@@ -38,45 +38,45 @@
__u16 hdr_len; /* 138 2 */
__u16 queue_mapping; /* 140 2 */
__u8 __cloned_offset[0]; /* 142 0 */
- __u8 cloned:1; /* 142: 7 1 */
- __u8 nohdr:1; /* 142: 6 1 */
- __u8 fclone:2; /* 142: 4 1 */
- __u8 peeked:1; /* 142: 3 1 */
- __u8 head_frag:1; /* 142: 2 1 */
- __u8 xmit_more:1; /* 142: 1 1 */
- __u8 pfmemalloc:1; /* 142: 0 1 */
+ __u8 cloned; /* 142 1 */
+ __u8 nohdr; /* 142 1 */
+ __u8 fclone; /* 142 1 */
+ __u8 peeked; /* 142 1 */
+ __u8 head_frag; /* 142 1 */
+ __u8 xmit_more; /* 142 1 */
+ __u8 pfmemalloc; /* 142 1 */
/* XXX 1 byte hole, try to pack */
__u32 headers_start[0]; /* 144 0 */
__u8 __pkt_type_offset[0]; /* 144 0 */
- __u8 pkt_type:3; /* 144: 5 1 */
- __u8 ignore_df:1; /* 144: 4 1 */
- __u8 nf_trace:1; /* 144: 3 1 */
- __u8 ip_summed:2; /* 144: 1 1 */
- __u8 ooo_okay:1; /* 144: 0 1 */
- __u8 l4_hash:1; /* 145: 7 1 */
- __u8 sw_hash:1; /* 145: 6 1 */
- __u8 wifi_acked_valid:1; /* 145: 5 1 */
- __u8 wifi_acked:1; /* 145: 4 1 */
- __u8 no_fcs:1; /* 145: 3 1 */
- __u8 encapsulation:1; /* 145: 2 1 */
- __u8 encap_hdr_csum:1; /* 145: 1 1 */
- __u8 csum_valid:1; /* 145: 0 1 */
- __u8 csum_complete_sw:1; /* 146: 7 1 */
- __u8 csum_level:2; /* 146: 5 1 */
- __u8 csum_not_inet:1; /* 146: 4 1 */
- __u8 dst_pending_confirm:1; /* 146: 3 1 */
- __u8 ndisc_nodetype:2; /* 146: 1 1 */
- __u8 ipvs_property:1; /* 146: 0 1 */
- __u8 inner_protocol_type:1; /* 147: 7 1 */
- __u8 remcsum_offload:1; /* 147: 6 1 */
- __u8 offload_fwd_mark:1; /* 147: 5 1 */
- __u8 offload_mr_fwd_mark:1; /* 147: 4 1 */
- __u8 tc_skip_classify:1; /* 147: 3 1 */
- __u8 tc_at_ingress:1; /* 147: 2 1 */
- __u8 tc_redirected:1; /* 147: 1 1 */
- __u8 tc_from_ingress:1; /* 147: 0 1 */
+ __u8 pkt_type; /* 144 1 */
+ __u8 ignore_df; /* 144 1 */
+ __u8 nf_trace; /* 144 1 */
+ __u8 ip_summed; /* 144 1 */
+ __u8 ooo_okay; /* 144 1 */
+ __u8 l4_hash; /* 145 1 */
+ __u8 sw_hash; /* 145 1 */
+ __u8 wifi_acked_valid; /* 145 1 */
+ __u8 wifi_acked; /* 145 1 */
+ __u8 no_fcs; /* 145 1 */
+ __u8 encapsulation; /* 145 1 */
+ __u8 encap_hdr_csum; /* 145 1 */
+ __u8 csum_valid; /* 145 1 */
+ __u8 csum_complete_sw; /* 146 1 */
+ __u8 csum_level; /* 146 1 */
+ __u8 csum_not_inet; /* 146 1 */
+ __u8 dst_pending_confirm; /* 146 1 */
+ __u8 ndisc_nodetype; /* 146 1 */
+ __u8 ipvs_property; /* 146 1 */
+ __u8 inner_protocol_type; /* 147 1 */
+ __u8 remcsum_offload; /* 147 1 */
+ __u8 offload_fwd_mark; /* 147 1 */
+ __u8 offload_mr_fwd_mark; /* 147 1 */
+ __u8 tc_skip_classify; /* 147 1 */
+ __u8 tc_at_ingress; /* 147 1 */
+ __u8 tc_redirected; /* 147 1 */
+ __u8 tc_from_ingress; /* 147 1 */
__u16 tc_index; /* 148 2 */
/* XXX 2 bytes hole, try to pack */
$
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2018-12-03 19:44:16 +01:00
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2019-02-14 14:47:32 +01:00
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uint32_t btf_elf__get32(struct btf_elf *btf, uint32_t *p);
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btf_loader: Introduce a loader for the BTF format
Show 'struct list_head' from DWARF info:
$ pahole -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
Try to show it from BTF, on a file without it:
$ pahole -F btf -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
pahole: /home/acme/git/build/v4.20-rc5+/net/ipv4/tcp.o: No debugging information found
Encode BTF from the DWARF info:
$ pahole -J ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
Check that it is there:
$ readelf -SW ~/git/build/v4.20-rc5+/net/ipv4/tcp.o | grep BTF
readelf: /home/acme/git/build/v4.20-rc5+/net/ipv4/tcp.o: Warning: possibly corrupt ELF header - it has a non-zero program header offset, but no program headers
[136] .BTF PROGBITS 0000000000000000 101d0e 042edf 00 0 0 1
Now try again printing 'struct list_head' from the BTF info just
encoded:
$ pahole -F btf -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o 2> /dev/null
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
$
There is the bitfields case that BTF desn't have the bit_size info for
bitfield members that makes the output from dwarf to be different than
the one from BTF:
$ pahole -F btf -C sk_buff ~/git/build/v4.20-rc5+/net/ipv4/tcp.o > /tmp/sk_buff.btf
$ pahole -F dwarf -C sk_buff ~/git/build/v4.20-rc5+/net/ipv4/tcp.o > /tmp/sk_buff.dwarf
$ diff -u /tmp/sk_buff.dwarf /tmp/sk_buff.btf
--- /tmp/sk_buff.dwarf 2018-12-20 14:50:51.428653046 -0300
+++ /tmp/sk_buff.btf 2018-12-20 14:50:46.302601516 -0300
@@ -38,45 +38,45 @@
__u16 hdr_len; /* 138 2 */
__u16 queue_mapping; /* 140 2 */
__u8 __cloned_offset[0]; /* 142 0 */
- __u8 cloned:1; /* 142: 7 1 */
- __u8 nohdr:1; /* 142: 6 1 */
- __u8 fclone:2; /* 142: 4 1 */
- __u8 peeked:1; /* 142: 3 1 */
- __u8 head_frag:1; /* 142: 2 1 */
- __u8 xmit_more:1; /* 142: 1 1 */
- __u8 pfmemalloc:1; /* 142: 0 1 */
+ __u8 cloned; /* 142 1 */
+ __u8 nohdr; /* 142 1 */
+ __u8 fclone; /* 142 1 */
+ __u8 peeked; /* 142 1 */
+ __u8 head_frag; /* 142 1 */
+ __u8 xmit_more; /* 142 1 */
+ __u8 pfmemalloc; /* 142 1 */
/* XXX 1 byte hole, try to pack */
__u32 headers_start[0]; /* 144 0 */
__u8 __pkt_type_offset[0]; /* 144 0 */
- __u8 pkt_type:3; /* 144: 5 1 */
- __u8 ignore_df:1; /* 144: 4 1 */
- __u8 nf_trace:1; /* 144: 3 1 */
- __u8 ip_summed:2; /* 144: 1 1 */
- __u8 ooo_okay:1; /* 144: 0 1 */
- __u8 l4_hash:1; /* 145: 7 1 */
- __u8 sw_hash:1; /* 145: 6 1 */
- __u8 wifi_acked_valid:1; /* 145: 5 1 */
- __u8 wifi_acked:1; /* 145: 4 1 */
- __u8 no_fcs:1; /* 145: 3 1 */
- __u8 encapsulation:1; /* 145: 2 1 */
- __u8 encap_hdr_csum:1; /* 145: 1 1 */
- __u8 csum_valid:1; /* 145: 0 1 */
- __u8 csum_complete_sw:1; /* 146: 7 1 */
- __u8 csum_level:2; /* 146: 5 1 */
- __u8 csum_not_inet:1; /* 146: 4 1 */
- __u8 dst_pending_confirm:1; /* 146: 3 1 */
- __u8 ndisc_nodetype:2; /* 146: 1 1 */
- __u8 ipvs_property:1; /* 146: 0 1 */
- __u8 inner_protocol_type:1; /* 147: 7 1 */
- __u8 remcsum_offload:1; /* 147: 6 1 */
- __u8 offload_fwd_mark:1; /* 147: 5 1 */
- __u8 offload_mr_fwd_mark:1; /* 147: 4 1 */
- __u8 tc_skip_classify:1; /* 147: 3 1 */
- __u8 tc_at_ingress:1; /* 147: 2 1 */
- __u8 tc_redirected:1; /* 147: 1 1 */
- __u8 tc_from_ingress:1; /* 147: 0 1 */
+ __u8 pkt_type; /* 144 1 */
+ __u8 ignore_df; /* 144 1 */
+ __u8 nf_trace; /* 144 1 */
+ __u8 ip_summed; /* 144 1 */
+ __u8 ooo_okay; /* 144 1 */
+ __u8 l4_hash; /* 145 1 */
+ __u8 sw_hash; /* 145 1 */
+ __u8 wifi_acked_valid; /* 145 1 */
+ __u8 wifi_acked; /* 145 1 */
+ __u8 no_fcs; /* 145 1 */
+ __u8 encapsulation; /* 145 1 */
+ __u8 encap_hdr_csum; /* 145 1 */
+ __u8 csum_valid; /* 145 1 */
+ __u8 csum_complete_sw; /* 146 1 */
+ __u8 csum_level; /* 146 1 */
+ __u8 csum_not_inet; /* 146 1 */
+ __u8 dst_pending_confirm; /* 146 1 */
+ __u8 ndisc_nodetype; /* 146 1 */
+ __u8 ipvs_property; /* 146 1 */
+ __u8 inner_protocol_type; /* 147 1 */
+ __u8 remcsum_offload; /* 147 1 */
+ __u8 offload_fwd_mark; /* 147 1 */
+ __u8 offload_mr_fwd_mark; /* 147 1 */
+ __u8 tc_skip_classify; /* 147 1 */
+ __u8 tc_at_ingress; /* 147 1 */
+ __u8 tc_redirected; /* 147 1 */
+ __u8 tc_from_ingress; /* 147 1 */
__u16 tc_index; /* 148 2 */
/* XXX 2 bytes hole, try to pack */
$
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2018-12-03 19:44:16 +01:00
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2019-02-14 14:47:32 +01:00
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void *btf_elf__get_buffer(struct btf_elf *btf);
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btf_loader: Introduce a loader for the BTF format
Show 'struct list_head' from DWARF info:
$ pahole -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
Try to show it from BTF, on a file without it:
$ pahole -F btf -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
pahole: /home/acme/git/build/v4.20-rc5+/net/ipv4/tcp.o: No debugging information found
Encode BTF from the DWARF info:
$ pahole -J ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
Check that it is there:
$ readelf -SW ~/git/build/v4.20-rc5+/net/ipv4/tcp.o | grep BTF
readelf: /home/acme/git/build/v4.20-rc5+/net/ipv4/tcp.o: Warning: possibly corrupt ELF header - it has a non-zero program header offset, but no program headers
[136] .BTF PROGBITS 0000000000000000 101d0e 042edf 00 0 0 1
Now try again printing 'struct list_head' from the BTF info just
encoded:
$ pahole -F btf -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o 2> /dev/null
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
$
There is the bitfields case that BTF desn't have the bit_size info for
bitfield members that makes the output from dwarf to be different than
the one from BTF:
$ pahole -F btf -C sk_buff ~/git/build/v4.20-rc5+/net/ipv4/tcp.o > /tmp/sk_buff.btf
$ pahole -F dwarf -C sk_buff ~/git/build/v4.20-rc5+/net/ipv4/tcp.o > /tmp/sk_buff.dwarf
$ diff -u /tmp/sk_buff.dwarf /tmp/sk_buff.btf
--- /tmp/sk_buff.dwarf 2018-12-20 14:50:51.428653046 -0300
+++ /tmp/sk_buff.btf 2018-12-20 14:50:46.302601516 -0300
@@ -38,45 +38,45 @@
__u16 hdr_len; /* 138 2 */
__u16 queue_mapping; /* 140 2 */
__u8 __cloned_offset[0]; /* 142 0 */
- __u8 cloned:1; /* 142: 7 1 */
- __u8 nohdr:1; /* 142: 6 1 */
- __u8 fclone:2; /* 142: 4 1 */
- __u8 peeked:1; /* 142: 3 1 */
- __u8 head_frag:1; /* 142: 2 1 */
- __u8 xmit_more:1; /* 142: 1 1 */
- __u8 pfmemalloc:1; /* 142: 0 1 */
+ __u8 cloned; /* 142 1 */
+ __u8 nohdr; /* 142 1 */
+ __u8 fclone; /* 142 1 */
+ __u8 peeked; /* 142 1 */
+ __u8 head_frag; /* 142 1 */
+ __u8 xmit_more; /* 142 1 */
+ __u8 pfmemalloc; /* 142 1 */
/* XXX 1 byte hole, try to pack */
__u32 headers_start[0]; /* 144 0 */
__u8 __pkt_type_offset[0]; /* 144 0 */
- __u8 pkt_type:3; /* 144: 5 1 */
- __u8 ignore_df:1; /* 144: 4 1 */
- __u8 nf_trace:1; /* 144: 3 1 */
- __u8 ip_summed:2; /* 144: 1 1 */
- __u8 ooo_okay:1; /* 144: 0 1 */
- __u8 l4_hash:1; /* 145: 7 1 */
- __u8 sw_hash:1; /* 145: 6 1 */
- __u8 wifi_acked_valid:1; /* 145: 5 1 */
- __u8 wifi_acked:1; /* 145: 4 1 */
- __u8 no_fcs:1; /* 145: 3 1 */
- __u8 encapsulation:1; /* 145: 2 1 */
- __u8 encap_hdr_csum:1; /* 145: 1 1 */
- __u8 csum_valid:1; /* 145: 0 1 */
- __u8 csum_complete_sw:1; /* 146: 7 1 */
- __u8 csum_level:2; /* 146: 5 1 */
- __u8 csum_not_inet:1; /* 146: 4 1 */
- __u8 dst_pending_confirm:1; /* 146: 3 1 */
- __u8 ndisc_nodetype:2; /* 146: 1 1 */
- __u8 ipvs_property:1; /* 146: 0 1 */
- __u8 inner_protocol_type:1; /* 147: 7 1 */
- __u8 remcsum_offload:1; /* 147: 6 1 */
- __u8 offload_fwd_mark:1; /* 147: 5 1 */
- __u8 offload_mr_fwd_mark:1; /* 147: 4 1 */
- __u8 tc_skip_classify:1; /* 147: 3 1 */
- __u8 tc_at_ingress:1; /* 147: 2 1 */
- __u8 tc_redirected:1; /* 147: 1 1 */
- __u8 tc_from_ingress:1; /* 147: 0 1 */
+ __u8 pkt_type; /* 144 1 */
+ __u8 ignore_df; /* 144 1 */
+ __u8 nf_trace; /* 144 1 */
+ __u8 ip_summed; /* 144 1 */
+ __u8 ooo_okay; /* 144 1 */
+ __u8 l4_hash; /* 145 1 */
+ __u8 sw_hash; /* 145 1 */
+ __u8 wifi_acked_valid; /* 145 1 */
+ __u8 wifi_acked; /* 145 1 */
+ __u8 no_fcs; /* 145 1 */
+ __u8 encapsulation; /* 145 1 */
+ __u8 encap_hdr_csum; /* 145 1 */
+ __u8 csum_valid; /* 145 1 */
+ __u8 csum_complete_sw; /* 146 1 */
+ __u8 csum_level; /* 146 1 */
+ __u8 csum_not_inet; /* 146 1 */
+ __u8 dst_pending_confirm; /* 146 1 */
+ __u8 ndisc_nodetype; /* 146 1 */
+ __u8 ipvs_property; /* 146 1 */
+ __u8 inner_protocol_type; /* 147 1 */
+ __u8 remcsum_offload; /* 147 1 */
+ __u8 offload_fwd_mark; /* 147 1 */
+ __u8 offload_mr_fwd_mark; /* 147 1 */
+ __u8 tc_skip_classify; /* 147 1 */
+ __u8 tc_at_ingress; /* 147 1 */
+ __u8 tc_redirected; /* 147 1 */
+ __u8 tc_from_ingress; /* 147 1 */
__u16 tc_index; /* 148 2 */
/* XXX 2 bytes hole, try to pack */
$
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2018-12-03 19:44:16 +01:00
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2019-02-14 14:47:32 +01:00
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size_t btf_elf__get_size(struct btf_elf *btf);
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btf_loader: Introduce a loader for the BTF format
Show 'struct list_head' from DWARF info:
$ pahole -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
Try to show it from BTF, on a file without it:
$ pahole -F btf -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
pahole: /home/acme/git/build/v4.20-rc5+/net/ipv4/tcp.o: No debugging information found
Encode BTF from the DWARF info:
$ pahole -J ~/git/build/v4.20-rc5+/net/ipv4/tcp.o
Check that it is there:
$ readelf -SW ~/git/build/v4.20-rc5+/net/ipv4/tcp.o | grep BTF
readelf: /home/acme/git/build/v4.20-rc5+/net/ipv4/tcp.o: Warning: possibly corrupt ELF header - it has a non-zero program header offset, but no program headers
[136] .BTF PROGBITS 0000000000000000 101d0e 042edf 00 0 0 1
Now try again printing 'struct list_head' from the BTF info just
encoded:
$ pahole -F btf -C list_head ~/git/build/v4.20-rc5+/net/ipv4/tcp.o 2> /dev/null
struct list_head {
struct list_head * next; /* 0 8 */
struct list_head * prev; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
$
There is the bitfields case that BTF desn't have the bit_size info for
bitfield members that makes the output from dwarf to be different than
the one from BTF:
$ pahole -F btf -C sk_buff ~/git/build/v4.20-rc5+/net/ipv4/tcp.o > /tmp/sk_buff.btf
$ pahole -F dwarf -C sk_buff ~/git/build/v4.20-rc5+/net/ipv4/tcp.o > /tmp/sk_buff.dwarf
$ diff -u /tmp/sk_buff.dwarf /tmp/sk_buff.btf
--- /tmp/sk_buff.dwarf 2018-12-20 14:50:51.428653046 -0300
+++ /tmp/sk_buff.btf 2018-12-20 14:50:46.302601516 -0300
@@ -38,45 +38,45 @@
__u16 hdr_len; /* 138 2 */
__u16 queue_mapping; /* 140 2 */
__u8 __cloned_offset[0]; /* 142 0 */
- __u8 cloned:1; /* 142: 7 1 */
- __u8 nohdr:1; /* 142: 6 1 */
- __u8 fclone:2; /* 142: 4 1 */
- __u8 peeked:1; /* 142: 3 1 */
- __u8 head_frag:1; /* 142: 2 1 */
- __u8 xmit_more:1; /* 142: 1 1 */
- __u8 pfmemalloc:1; /* 142: 0 1 */
+ __u8 cloned; /* 142 1 */
+ __u8 nohdr; /* 142 1 */
+ __u8 fclone; /* 142 1 */
+ __u8 peeked; /* 142 1 */
+ __u8 head_frag; /* 142 1 */
+ __u8 xmit_more; /* 142 1 */
+ __u8 pfmemalloc; /* 142 1 */
/* XXX 1 byte hole, try to pack */
__u32 headers_start[0]; /* 144 0 */
__u8 __pkt_type_offset[0]; /* 144 0 */
- __u8 pkt_type:3; /* 144: 5 1 */
- __u8 ignore_df:1; /* 144: 4 1 */
- __u8 nf_trace:1; /* 144: 3 1 */
- __u8 ip_summed:2; /* 144: 1 1 */
- __u8 ooo_okay:1; /* 144: 0 1 */
- __u8 l4_hash:1; /* 145: 7 1 */
- __u8 sw_hash:1; /* 145: 6 1 */
- __u8 wifi_acked_valid:1; /* 145: 5 1 */
- __u8 wifi_acked:1; /* 145: 4 1 */
- __u8 no_fcs:1; /* 145: 3 1 */
- __u8 encapsulation:1; /* 145: 2 1 */
- __u8 encap_hdr_csum:1; /* 145: 1 1 */
- __u8 csum_valid:1; /* 145: 0 1 */
- __u8 csum_complete_sw:1; /* 146: 7 1 */
- __u8 csum_level:2; /* 146: 5 1 */
- __u8 csum_not_inet:1; /* 146: 4 1 */
- __u8 dst_pending_confirm:1; /* 146: 3 1 */
- __u8 ndisc_nodetype:2; /* 146: 1 1 */
- __u8 ipvs_property:1; /* 146: 0 1 */
- __u8 inner_protocol_type:1; /* 147: 7 1 */
- __u8 remcsum_offload:1; /* 147: 6 1 */
- __u8 offload_fwd_mark:1; /* 147: 5 1 */
- __u8 offload_mr_fwd_mark:1; /* 147: 4 1 */
- __u8 tc_skip_classify:1; /* 147: 3 1 */
- __u8 tc_at_ingress:1; /* 147: 2 1 */
- __u8 tc_redirected:1; /* 147: 1 1 */
- __u8 tc_from_ingress:1; /* 147: 0 1 */
+ __u8 pkt_type; /* 144 1 */
+ __u8 ignore_df; /* 144 1 */
+ __u8 nf_trace; /* 144 1 */
+ __u8 ip_summed; /* 144 1 */
+ __u8 ooo_okay; /* 144 1 */
+ __u8 l4_hash; /* 145 1 */
+ __u8 sw_hash; /* 145 1 */
+ __u8 wifi_acked_valid; /* 145 1 */
+ __u8 wifi_acked; /* 145 1 */
+ __u8 no_fcs; /* 145 1 */
+ __u8 encapsulation; /* 145 1 */
+ __u8 encap_hdr_csum; /* 145 1 */
+ __u8 csum_valid; /* 145 1 */
+ __u8 csum_complete_sw; /* 146 1 */
+ __u8 csum_level; /* 146 1 */
+ __u8 csum_not_inet; /* 146 1 */
+ __u8 dst_pending_confirm; /* 146 1 */
+ __u8 ndisc_nodetype; /* 146 1 */
+ __u8 ipvs_property; /* 146 1 */
+ __u8 inner_protocol_type; /* 147 1 */
+ __u8 remcsum_offload; /* 147 1 */
+ __u8 offload_fwd_mark; /* 147 1 */
+ __u8 offload_mr_fwd_mark; /* 147 1 */
+ __u8 tc_skip_classify; /* 147 1 */
+ __u8 tc_at_ingress; /* 147 1 */
+ __u8 tc_redirected; /* 147 1 */
+ __u8 tc_from_ingress; /* 147 1 */
__u16 tc_index; /* 148 2 */
/* XXX 2 bytes hole, try to pack */
$
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2018-12-03 19:44:16 +01:00
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2018-03-06 01:53:50 +01:00
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#endif /* _LIBBTF_H */
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